(Bloomberg) -- Premiums for gold coins are staying at highly elevated levels for longer than ever before, as investors flock to bullion at a time when physical-supply flows are disrupted.

American Eagle gold coins are selling for about 5% above the spot price of bullion, the most since the 2016 Brexit vote, according to Everett Millman, a precious-metals specialist at Gainesville Coins in Florida. That’s about double the regular premium and has stayed at such levels for two weeks, he said.

Spot gold is currently trading down about 1% near $1,614 an ounce, after rising the past three sessions. Bullion futures also fell to settle at $1,634.30.

Along with surging prices, the dealer is facing a month-long delivery backlog as precious metal supply chains take a hit during the outbreak of the coronavirus around the world. Bullion has been especially in demand from investors seeking a haven from global market turmoil.

“When you look at a jump in the premium like that, that’s definitely an indication that demand is higher than supply,” Millman said. “All the supply chains are backed up for at least a month.”

The situation is not specific to Gainesville Coins, he said. “I’ve seen that with virtually every dealer in the country.”

As recently as two weeks ago, premiums for gold coins were at of 1% or 2%, according to Millman. Silver coins are also in demand, with premiums for that metal at 50% over the spot price, compared with just 5% a couple of weeks earlier.

Read more: Silver Coins Sell Out With Retail Buyers Stocking Up for Crisis

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